scispace - formally typeset
Search or ask a question
Topic

Electrical impedance

About: Electrical impedance is a research topic. Over the lifetime, 36015 publications have been published within this topic receiving 371891 citations. The topic is also known as: electrical impedance & complex impedance.


Papers
More filters
Patent
13 Mar 1998
TL;DR: In this paper, a power conversion circuit is proposed to drive a cold cathode fluorescent lamp (CCFL) while requiring minimal number of external components, including a controller, a direct drive network responsive to control inputs from the controller and coupled to receive a power signal, and a secondary network coupled to the CCFL.
Abstract: A power conversion circuit drives a cold cathode fluorescent lamp (CCFL) while requiring minimal number of external components. The circuit includes a controller, a direct drive network responsive to control inputs from the controller and coupled to receive a power signal, and a secondary network coupled to the CCFL. The direct drive network is low Q circuit comprising a plurality of switching transistors and a primary winding of a transformer such that an impedance of the direct drive network consists essentially of an inductance of the primary winding and capacitance of the direct drive network consists essentially of parasitic capacitance reflected from the secondary winding. The Q of the direct drive network is less than about 0.5 so that a square wave voltage signal is provided across the primary winding of the transformer. However, the inductance of the transformer is sufficiently high such that the voltage across a secondary winding of the transformer is sinusoidal. The secondary network comprises the secondary winding of the transformer coupled to the CCFL through a connector to provide a sinusoidal current to the CCFL. The controller controls the current passing through the CCFL by pulse width modulating the control inputs to the direct drive network.

99 citations

Journal ArticleDOI
TL;DR: In this article, the effect of artificial magneto-dielectric substrates on the impedance bandwidth properties of microstrip antennas is discussed, and a realistic dispersive behavior of a practically realizable artificial substrate is embedded into the model, and it is shown that frequency dispersion of the substrate plays a very important role in impedance bandwidth characteristics of the loaded antenna.
Abstract: In the present paper we discuss the effect of artificial magneto-dielectric substrates on the impedance bandwidth properties of microstrip antennas. The results found in the literature for antenna miniaturization using magnetic or magneto-dielectric substrates are revised, and discussion is addressed to the practically realizable artificial magnetic media operating in the microwave regime. Using a transmission-line model we, first, reproduce the known results for antenna miniaturization with non-dispersive material fillings. Next, a realistic dispersive behavior of a practically realizable artificial substrate is embedded into the model, and we show that frequency dispersion of the substrate plays a very important role in the impedance bandwidth characteristics of the loaded antenna. The impedance bandwidths of reduced size patch antennas loaded with dispersive magneto-dielectric substrates and high-permittivity substrates are compared. It is shown that unlike substrates with dispersion-free permeability, practically realizable artificial substrates with dispersive magnetic permeability are not advantageous in antenna miniaturization. This conclusion is experimentally validated.

99 citations

Journal ArticleDOI
20 Jun 1993
TL;DR: In this paper, the standard current loop is modified for a boost power converter to eliminate sensitivity of the control-to-output transfer function to the nature and magnitude of resistive load.
Abstract: The standard current loop is modified for a boost power converter to eliminate sensitivity of the control-to-output transfer function to the nature and magnitude of resistive load. An additional term directly proportional to the load current and output voltage, and inversely proportional to the input voltage is added to the current loop. This results in practically invariant loop gains for different resistive loads, including constant power load. >

99 citations

Journal ArticleDOI
TL;DR: In this paper, the authors developed dc impedance models for the rectifier and inverter stations for a VSC-HVDC system when they are viewed from a dc terminal.
Abstract: Resonances can have a negative impact on a voltage-source converter–high voltage dc (VSC–HVDC) system. This paper develops dc impedance models for the rectifier and inverter stations for a VSC-HVDC system when they are viewed from a dc terminal. The impedance models take converter controllers into account. The derived impedance models are validated by comparing frequency responses of the analytical model and the impedance measured at the dc terminal from a detailed VSC–HVDC model simulated in a real-time digital simulator. Resonances are examined in the frequency domain (e.g., Bode plots and Nyquist plots) using the derived analytical impedance models. The analysis is verified by time-domain simulations. Real-time digital simulation in RT-Lab demonstrates that the dc capacitor has a significant impact on resonances while the power transfer level has an insignificant impact on resonances.

99 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used maximum length sequences (MLS) for periodic excitation signal in a microfluidic impedance cytometer, which allowed multi-frequency single cell impedance measurements to be made in a short time period.
Abstract: Measurements of the dielectric (or impedance) properties of cells can be used as a general characterization and diagnostic tool. In this paper, we describe a novel impedance spectroscopy technique for the analysis of single biological cells in suspension. The technique uses maximum length sequences (MLS) for periodic excitation signal in a microfluidic impedance cytometer. The method allows multi-frequency single cell impedance measurements to be made in a short time period (ms). Spectral information is obtained in the frequency domain by applying a fast M-sequence transform (FMT) and fast Fourier transform (FFT) to the time domain response. Theoretically, the impedance is determined from the transfer function of the system when the MLS is a current excitation. The order of the MLS and sampling rate of A/D conversion are two factors that determine the bandwidth and spectral accuracy of the technique. Experimentally, the applicability of the technique is demonstrated by characterizing the impedance spectrum of red blood cells (RBCs) in a microfluidic cytometer. The impedance is measured within 1 ms at 512 discrete frequencies, evenly distributed in the range from 976.56 Hz to 500 kHz. The measured spectrum shows good agreement with simulations.

98 citations


Network Information
Related Topics (5)
Voltage
296.3K papers, 1.7M citations
87% related
Capacitor
166.6K papers, 1.4M citations
85% related
Amplifier
163.9K papers, 1.3M citations
85% related
Dielectric
169.7K papers, 2.7M citations
81% related
Electromagnetic coil
187.8K papers, 1.1M citations
80% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,514
20223,479
20211,009
20201,579
20191,924
20181,809